[linux-lvm] root filesystem snapshots

[rich turner <rich storix com>]

in the past i have read a number of posts related to problems with doing
snapshots of logical volumes that contain the root filesystem. i am able
to replicate the problem here as well, the system just hangs. can anyone
tell me specifically what the problem relates to and if there is a fix
available? i have downloaded the latest LVM2 source and there is no
mention of it in WHATS_NEW.

i would like to warn people should they decide to do a snapshot of a
logical volume that contains the root filesystem. under what
circumstances will i run into this problem?
is it a certain level of LVM?
a certain level of the kernel?
a certain level of device-mapper?
a certain filesystem type?

also, i have seen problems with doing snapshots of filesystems using
ext3. i assume this is related to the VFS lock patch. should i be able
to perform snapshots of ext3 filesystems without failure?